THE 12-WEEK EFFECT OF CHANGE IN BODY WEIGHT AND BODY COMPOSITION ON MUSCULAR STRENGTH AND FUNCTION IN OVERWEIGHT ADULTS. Kimberly Anne Weary

Transcription

1 THE 12-WEEK EFFECT OF CHANGE IN BODY WEIGHT AND BODY COMPOSITION ON MUSCULAR STRENGTH AND FUNCTION IN OVERWEIGHT ADULTS By Kimberly Anne Weary B.S., Slippery Rock University, 2003 Submitted to the Graduate Faculty of the School of Education in partial fulfillment of the requirements for the degree of Master of Science University of Pittsburgh 2005

2 UNIVERSITY OF PITTSBURGH SCHOOL OF EDUCATION This thesis was presented by Kimberly Anne Weary It was defended on December 13, 2005 and approved by Amy Otto, Ph.D. Bret Goodpaster, Ph.D. John M. Jakicic, Ph.D. Thesis Director ii

3 Copyright by Kimberly Anne Weary 2005 iii

4 THE 12-WEEK EFFECT OF CHANGE IN BODY WEIGHT AND BODY COMPOSITION ON MUSCULAR STRENGTH AND FUNCTION IN OVERWEIGHT ADULTS Kimberly Anne Weary, B.S. University of Pittsburgh, 2005 PURPOSE: The purpose of this study is to examine the relationship between the changes in body weight and lean body mass with changes in muscular strength and function in overweight and obese adults before and after a 12 week weight loss intervention. METHODS: Fifty-seven overweight adults ( % body fat) participated in this study. Forty eight subjects completed the 12 week weight loss intervention consisting of weekly behavioral counseling and the use of the HealthWear System, a computer-based monitoring system that objectively measures energy expenditure. Before and after this 12 week intervention, body weight, body mass index (BMI), body composition, muscular strength (1-RM chest press, 1-RM leg extension, grip strength), and function (sit-to-stand) were measured. RESULTS: Paired sample T-tests revealed a significant decrease in body weight, lean body mass, 1-RM chest press, and 1-RM leg extension and a significant increase in function from baseline to week 12 (Table 1). There was no significant change in grip strength from baseline to week 12. Correlation analyses revealed a moderate negative correlation between the percent change in body weight and the change in function (r = -.352). Table 1. Baseline 12 Weeks Change p-value Weight (kg) <.001 LBM (kg) RM chest (kg) RM leg (kg) <0.001 Grip Strength (kg) Sit-to-Stand CONCLUSION: Although LBM and strength decreased during this 12 week intervention, weight loss produced a marked improvement in function. This is an important finding because function can improve during weight loss regardless of resistance training. Improved function can potentially create a higher quality of life and longer independent living in individuals who lose approximately 6% of their total body weight. iv

5 TABLE OF CONTENTS 1.0 INTRODUCTION RATIONALE/SIGNIFICANCE SPECIFIC AIMS RESEARCH HYPOTHESES LITERATURE REVIEW OBESITY PREVELANCE RISKS ASSOCIATED WITH OBESITY BEHAVIORAL WEIGHT LOSS INTERVENTIONS EFFECTS OF WEIGHT LOSS ON LBM EFFECTS OF WEIGHT LOSS ON MUSCULAR STRENGTH EFFECTS OF WEIGHT LOSS ON FUNCTIONAL PERFORMANCE METHODS SUBJECTS EXCLUSION CRITERIA RECRUITMENT EXPERIMENTAL DESIGN INTERVENTION COMPONENTS Intervention Contact Behavioral Lesson Content DIETARY INTERVENTION EXERCISE RECOMMENDATIONS ASSESSMENT PROCEDURES DATA ANALYSIS POWER ANALYSIS v

6 4.0 RESULTS SUBJECT CHARACTERISTICS RETENTION RATES ABSOLUTE AND RELATIVE CHANGES Absolute and Relative Change in Body Weight and Lean Body Mass Absolute and Relative Change in Strength and Function Absolute and Relative Change in Leisure Time Physical Activity RESULTS OF CORRELATIONAL ANALYSES Change in Body Weight and Muscular Strength Change in Body Weight and Function Change in LBM and Muscular Strength Change in LBM and Function Change in Muscular Strength and Function Leisure Time Physical Activity and Strength and Function SUMMARY OF RESULTS CONCLUSION INTRODUCTION DISCUSSION OF RESULTS Effect of Intervention on Weight Loss Effect of Weight Loss on Lean Body Mass Effect of Weight Loss on Changes in Muscle Strength Effect of Weight Loss on Physical Function RECOMMENDATIONS FUTURE RESEARCH SUMMARY REFERENCES APPENDIX A APPENDIX B APPENDIX C APPENDIX D APPENDIX E vi

7 LIST OF TABLES Table 3.1 Behavioral Lesson Titles Table 4.1 Subject Characteristics Table 4.2 Change in Weight, Lean Body Mass, Strength, and Function Table 4.3 Correlation between Change in Weight & LBM and Change in Strength & Function.30 Table 4.4 Correlation between Leisure Time Physical Activity and Strength and Function vii

8 LIST OF FIGURES Figure 4.1 Retention Rates viii

9 I. INTRODUCTION 1.0 Introduction A significant public health problem in the United States is related to excess body weight. It is estimated that in excess of 60 percent of adults in the United States are overweight, which is defined as a body mass index (BMI) of a least 25 kg/m 2 (Flegal et al, 1998). Moreover, in excess of 30 percent of adults are classified as obese (BMI > 30 kg/m 2 ). These percentages have risen significantly over the past few decades (Kuczmarski, Flegal, Campbell, & Johnson, 1994), despite the addition of surgical, pharmacotherapy, and enhanced behavioral interventions to address this health concern. Excess amounts of weight can contribute to health complications that increase mortality. It is estimated that overweight and obesity contribute to approximately 325,000 deaths per year (Allison et al, 1999). In addition, obesity increases the risk of various chronic diseases such as heart disease, diabetes, and cancer (Rimm et al, 1995; Wing et al, 1999), which may be a result of increases in risk factors such as hypertension, hyperlipidemia, and insulin resistance. Recent data indicates that the direct cost of treating these obesity-related conditions in the United States has been estimated to be $70 billion, or 7% of health care expenditures, while indirect costs are estimated to be $48 billion (Colditz, 1999). These health care costs may actually be an underestimation of the actual cost because the impact of reduced physical functioning is not considered in the estimate (Coakley et al, 1998). These factors support the need to develop effective interventions to address the public health implications of obesity. Effective interventions for weight loss are focused on creating an energy deficit, with the most effective behavioral interventions combining a reduction in energy intake (diet) with an increase in energy expenditure (physical activity) (Wing, 2001). It has been demonstrated that behavioral interventions which combine these two components typically result in weight loss of 1

10 approximately 10 percent of initial body weight over a 5 to 6 month period (Wing, 1998), and this can significantly improve health-related outcomes (Agurs-Collins et al, 1997; Wing et al, 1987; & Torjeson et al, 1997). However, it appears that loss of lean body mass contributes 10 to 47 percent of the total weight loss typically observed with behavioral interventions (Ross et al, 1996; Trombetta et al, 2003; Bryner et al, 1999; Byrne et al, 2003; & Lynch et al, 2000). There is a body of literature which demonstrated the potential negative influence of the reductions in lean body mass on physiological and metabolic factors that may impact initial weight loss and long-term weight loss maintenance. A primary focus of research has been on the potential contribution of the loss of lean body mass on the reductions in resting energy expenditure typically observed with weight loss (Ross et al, 1996; Trombetta et al, 2003; Bryner et al, 1999; Byrne et al, 2003; Donnelly et al, 1991; Lynch et al, 2000). It has been demonstrated that resting energy expenditure is correlated with absolute level of lean body mass (Ross et al, 1996; Byrne et al, 2003; & Bryner et al, 1999). This has lead to some evidence that the reductions in lean body mass that may occur with weight loss at least partially contributes to the concurrent reduction in resting energy expenditure that is typically observed (Ross et al, 1996; Trombetta et al, 2003; Bryner et al, 1999; Byrne et al, 2003; Donnelly et al, 1991). There is also evidence that the quality of the lean body mass may contribute to metabolic pathways that contribute to glucose control, insulin sensitivity, and other parameters that may impact body weight regulation. This has partially contributed to a line of research focusing on potential interventions, such as resistance exercise, to minimize the loss of lean body mass and the concurrent physiological and metabolic factors that my impact body weight regulation (Ross et al, 1996; Ryan et al, 1995; Schmitz et al, 2002; Ballor et al, 1988; Bryner et al, 1999). Despite the potential physiological and metabolic benefits of maintaining the amount and/or quality of lean body mass with weight loss, there may be additional outcomes impacted by the 2

11 change in lean body mass typically observed with weight loss. It is widely believed that amount of lean body mass is positively correlated with muscular strength (Kraemer et al, 1999), and that increases in lean body mass resulting from restistance exercise will result in an increase in muscular strength. However, an understudied area is whether the loss of lean body mass with weight loss results in a concurrent reduction in muscular strength, and whether the loss of lean mass further contributes to potential changes in functional ability of overweight and obese adults. Moreover, it is unclear if observed changes in these variables are associated with perceived ability to perform common activities of daily living (ADL) or changes in perceived function according to life quality outcomes. This study will focus on documenting the observed and perceived changes in function that occur with weight loss, and will further examine the potential contribution change in lean body mass on these outcomes Rationale and Significance Several studies have shown that lean body mass is compromised during weight loss interventions (Ross et al, 1996; Kraemer et al, 1999). This decline in lean body mass may impact absolute and relative (based on body weight) measures of muscular strength. It has been found that subjects participating in weight loss regimens with combined diet and endurance exercise activities lose approximately 6% of their initial strength (Donnelly et al, 1991). Additional research in the geriatric population has warranted that muscle strength has been shown to correlate with overall functional performance as well as with performance at specific activities such as attaining a standing position, walking, and climbing stairs (Bohannon, 1992, and Hughes et al, 1996). If function is compromised due to a loss of lean body mass and strength during weight loss regimens, it would support the need for resistance exercise training to be incorporated into these weight loss interventions. Resistance training may not only be incorporated to spare the metabolic effects of 3

12 lean body mass, but to maintain or increase the functional performance related to lean body mass and strength Specific Aims Primary Specific Aims 1. To examine the relationship between the change in body weight and the change in muscular strength in overweight and obese individuals. 2. To examine the relationship between the change in lean body mass and the change in muscular strength in overweight and obese individuals. 3. To examine the relationship between the change in body weight and the change in functional ability in overweight and obese individuals. 4. To examine the relationship between the change in lean body mass and the change in functional ability in overweight and obese individuals. 5. To examine the relationship between the change in strength and the change in functional ability in overweight and obese individuals. 6. To examine the relationship between the change in leisure time physical activity and the change in functional ability in overweight and obese individuals. Secondary Specific Aims 7. To examine the effect of a 12-week weight loss program on absolute and relative changes in body weight in overweight and obese adults. 8. To examine the effect of a 12-week weight loss program on absolute and relative changes in lean body mass in overweight and obese adults. 9. To examine the effect of a 12-week weight loss program on absolute and relative changes in muscular strength in overweight and obese adults. 4

13 10. To examine the effect of a 12-week weight loss program on changes in functional ability in overweight and obese adults Research Hypotheses Primary Research Hypotheses 1. It is hypothesized that there will be a significant correlation between change in body weight and change in muscular strength in overweight and obese individuals. 2. It is hypothesized that there will be a significant correlation between change in lean body mass and change in muscular strength in overweight and obese individuals. 3. It is hypothesized that there will be a significant correlation between change in body weight and change in functional ability in overweight and obese individuals. 4. It is hypothesized that there will be a significant correlation between change in lean body mass and change in functional ability in overweight and obese individuals. 5. It is hypothesized that there will be a significant correlation between the change in strength and the change in functional ability in overweight and obese individuals. 6. It is hypothesized that there will be a significant correlation between change in leisure time physical activity and change in functional ability in overweight and obese individuals. Secondary Research Hypotheses 7. It is hypothesized that there will be absolute and relative changes in body weight in overweight and obese adults after a 12-week weight loss program. 8. It is hypothesized that there will be absolute and relative changes in lean body mass in overweight and obese adults after a 12-week weight loss program. 9. It is hypothesized that there will be absolute and relative changes in muscular strength in overweight and obese adults after a 12-week weight loss program. 5

14 10. It is hypothesized that there will be changes in functional ability in overweight and obese adults after a 12-week weight loss program. 6

15 II. LITERATURE REVIEW 2.1. Obesity Prevalence A significant public health problem in the United States is related to excess body weight. Currently, approximately 60 million U.S. adults are overweight. Moreover, in excess of 30 percent of adults are classified as obese (BMI >30 kg/m 2 ). These percentages have risen significantly over the past few decades (Kuczmarski, Flegal, Campbell, & Johnson, 1994) despite the addition of surgical, pharmacotherapy, and enhanced behavioral interventions to address this health concern Risks Associated with Obesity Overweight and obese individuals may display several risk factors of CHD such as hypertension, hyperlipidemia, and diabetes mellitus. Furthermore, obesity has been linked to other serious health problems such as musculoskeletal disorders and cancer (Tsai et al.). Since obesity is a demonstrated health risk factor for both men and women, it is a risk factor to be avoided. Arthur Leon (1987) suggests that it is a factor that is easier to avoid then to treat. Therefore, fat weight gain should be monitored and controlled before it develops into unmanageable obesity. One way of controlling or preventing body fat gain has been through exercise intervention. Exercise training programs have been effective in reducing percent body fat because they increase the individual s weekly kilocalorie output above previously sedentary levels. Thus, the purpose of this literature review will be to examine the effectiveness of weight loss interventions and to further examine their effect on muscle mass, muscle strength, and functional performance Behavioral Weight Loss Interventions Effective interventions for weight loss are focused on creating an energy deficit, with the most effective behavioral interventions combining a reduction in energy intake (diet) with an increase in energy expenditure (physical activity). Hagan et al. (1986) compared diet, exercise, and diet-plus-exercise in men and women for 12 weeks. Their results support the incorporation of both 7

16 diet and exercise in treatment programs and suggest that little change in body weight can be expected from exercise alone during a short-term intervention. In addition, Wood et al. (1991) reported significantly greater weight loss following a 1-year intervention in men participating in a diet-plus-exercise intervention compared with those receiving only a diet intervention (8.7 kg kg versus 5.1 kg kg). Furthermore, in a study conducted by Wing et al. (1988), she reported significantly greater weight loss in a diet-plus-exercise intervention compared with a diet intervention alone. After an additional year of less intensive intervention, the diet-plus-exercise group maintained an average weight loss of 7.9 kg versus 3.8 kg in the diet-only group Effects of Weight Loss on LBM However, there is some concern that a significant portion of this weight loss may be in the form of lean body mass. Ross et al. (2000) studied 52 obese men who were randomly assigned to one of four study groups: diet-induced weight loss, exercise-induced weight loss, exercise without weight loss, and control. After 20 weeks, Ross et al. found that skeletal muscle mass decreased by 5% (23% of total weight lost) in the diet-induced weight loss group but was unchanged in both exercise groups. In addition, Trombetta et al. (2003) studied the effects of a 4 month hypocaloric diet and a hypocaloric diet with exercise training (aerobic plus resistance training) on several different parameters in 59 obese women. Trombetta found that in the diet group, lean body mass was reduced by 10% (47.19% of total weight lost) whereas the diet plus exercise group only saw a 3% reduction in lean body mass (13.2% of total weight lost), which was not statistically significant. Because of observed reductions in lean body mass, research has focused on the potential influence of these changes on physiological factors that may impact initial weight loss and the longterm weight management. There is a significant body of literature which demonstrates a relationship between lean body mass and resting energy expenditure (Ross et al; Wadden et al; Byrne et al; & 8

17 Bryner et al), along with a body of literature which demonstrates that both lean body mass and resting energy expenditure decrease with weight loss (Ross et al; Trombetta et al; Bryner et al; Byrne et al; Donnelly et al; & Lynch et al). This has partially contributed to research focusing on potential interventions, such as resistance exercise, to minimize the loss of lean body mass and concurrent reductions observed in resting energy expenditure (Ross et al; Schmitz et al; Ballor et al; Ryan et al; & Bryner et al). Although resting energy expenditure is an important factor in weight loss, the purpose of this review will focus on the effects of LBM on function. Ross et al. (2000) found that diet-plus-exercise (aerobic exercise) did not preserve lean body mass and resting energy expenditure in a 12 week weight loss intervention study. Thus, it may be necessary to incorporate a resistance training program into a weight loss intervention to minimize the reduction in lean body mass and resting metabolic rate. This area of research however has had several different results and not all trials support this hypothesis. For example, Donnelly et al. (1991) studied 69 females for 90 days on a very low calorie diet. Each of these subjects was assigned to one of the following groups: diet only (C), diet plus endurance training (EE), diet plus weight training (WT), or diet plus endurance exercise and weight training (EEWT). Donnelly found that changes in body weight, percent fat, fat weight, and fat-free mass were not different between groups. Declines in resting metabolic rate (RMR) were approximately 7% to approximately 12% of baseline values with no differences among groups. Strength index showed declines of approximately 6% for C and EE and gains of approximately 3% and approximately 10% for EEWT and WT, respectively. This clinical trial did not show advantages of any exercise regimen over diet alone for weight loss, body-composition changes, or declines in RMR. On the other hand, Donnelly et a.l (1993) conducted a study to determine whether muscle hypertrophy is possible during a large-scale weight loss intervention. Fourteen obese females 9

18 received a 3360 kj/day liquid diet for 90 days. Seven subjects received a weight training (WT) regimen and seven subjects remained sedentary (C). Biopsy samples were obtained from the vastus lateralis muscle at baseline and after 90 days of treatment. The average weight loss over the 90 day period was 16 kg with approximately 24% of the weight loss from FFM and 76% from fat. The amount and composition of the weight loss did not differ between the WT and C groups. The crosssectional area of the slow twitch and fast twitch fibers was unchanged by treatment in C subjects but significantly increased with WT subjects. Thus, it appears that even though FFM may be compromised, weight training can produce hypertrophy in skeletal muscle during severe energy restriction and large-scale weight loss. Furthermore, Bryner et al. (1999) studied twenty subjects (17 women, 3 men), mean age 38 years, over 12 weeks. These subjects were randomly assigned to either a standard treatment control plus diet, or resistance exercise plus diet. The control plus diet group exercised for one hour four times/week by walking, biking, or stair climbing, whereas the resistance exercise plus diet group performed resistance training 3 days/week in the form of a circuit. Both groups consumed 800 kcal/day in the form of a liquid diet. At the end of the 12 weeks, it was found that the control plus diet group lost 4 kg of lean body mass (22% of total weight lost) whereas the resistance exercise plus diet group only lost.8 kg of lean body mass (5.5% of total weight lost) which was not statistically significant. Keim et al. (1990) examined the effects of exercise training and the influence of a moderate calorie restriction on the training response in ten overweight women over a 14 week period. After a 2 week stabilization period, in which diets were designed to maintain body weight (BW), five women were assigned to a 12 week experimental program of diet and exercise (D+EX) that included a 50% reduction in energy intake and a program of moderate intensity aerobic exercise 6 days/week. The other five women were assigned to the same daily exercise (EX) and continued to consume the 10

19 stabilization diet. Periodic measurements of resting metabolic rate (RMR), thermic effect of food (TEF), energy cost of exercise, and predicted maximal aerobic capacity were obtained. Body composition was monitored weekly. Tests of strength and anaerobic capacity were conducted. D+EX lost an average of approximately 1.1 kg of body weight per week, which was 67% fat and 33% lean weight. EX lost approximately 0.5 kg/wk, which was 86% fat and 14% lean. The RMR declined 9% in the D+EX group, whereas it was maintained in the EX group Effect of Weight Loss on Muscular Strength In addition to the loss of LBM and a reduction in RMR during weight loss regimens, Donnelly has also found that subjects participating in regimens with combined diet and endurance exercise activities lose approximately 6% of their initial strength (Donnelly, 1994). It is important to determine the effect of this absolute and/or relative strength loss on the change of functional performance, both measured and perceived, to observe changes in the ability to perform activities of daily living. Pronk et al. (1992) determined strength changes induced by very low-calorie diet (VLCD, 520 kcal/day) alone and in combination with exercise in 109 severely obese females (46.8 +/- 4.69% fat). Experimental treatments included VLCD alone, VLCD with endurance exercise (EE), VLCD with endurance exercise and resistance strength training (EERST), and VLCD with resistance strength training (RST). All subjects participated in the study for 90 days while EE, EERST, and RST exercised 4 times/week according to specified schedules. Results indicated significant differences for the change scores (baseline to 90 days) for bench press, knee flexion, upper body and lower body composite strength scores between RST and all the other groups. RST was the only treatment group that increased upper and lower body strength. No differences between groups were found for body mass losses, decrease in percent fat and fat mass. In contrast, these variables showed significant change scores for all groups. Decreases in fat-free mass (FFM) were /- 3.4 kg, 11

20 4.79 +/ kg, / kg, and / kg for EE, LC, RST, and EERST, respectively. These data suggest that the combination of resistance strength training and VLCD increases strength despite a loss of FFM. However, endurance exercise and VLCD do not seem to affect body mass loss or FFM loss per se. Moreover, it seems that these increases in strength may represent a training effect which might imply improved central neuromuscular function rather than muscular hypertrophy since FFM decreased in all groups. It is important to determine whether this strength loss is due to absolute changes in strength or relative changes in strength. If absolute strength is compromised during a weight loss intervention, the participant may still be able to maintain and/or improve function if the ratio between weight lost and strength lost is high. However, if the participant loses strength relative to body weight, this could impede upon the participant s functional performance Effect of Weight Loss on Functional Performance A related area of research that is understudied is the potential impact of loss of body weight, lean body mass, and muscular strength on functional ability and functional performance in overweight and obese individuals. Moreover, it is unclear if observed changes in these variables are associated with perceived ability to perform common activities of daily living (ADL) or changes in health-related quality of life (HRQL). Since the effect of weight loss on functional performance has been understudied in the overweight and obese population, it is imperative to look at a population in which functional performance has been studied; the elderly population. One of the primary consequences of aging, a consequence which leads to significantly impaired function in the elderly population, is the loss of skeletal muscle strength and mass. Both of these decrease up to one-third in humans between the ages of 30 and 80 years (Barton-Davis et al, 1998). 12

21 Aging typically leads to an increase in body fat and a decrease in lean body mass (LBM). Alterations in muscle mass can reflect other changes such as a decrease in strength, functional ability, and resting metabolic rate. Maintaining a balance between fat and muscle mass throughout life is crucial because the loss of muscle mass is implicated in variables of metabolic rate and physical activity and increases in body fat are associated with type II diabetes, hypertension, certain cancers, and coronary artery disease (Rogers et al, 1993). Muscle mass leads to a reduction in muscle function; therefore, muscle mass should be maintained throughout life to maintain function (Kirkendall, 1998). Harris (1997) suggests that in relatively sedentary populations, such as the elderly, a major determinant of muscle mass is body weight. Furthermore, Forbes (1987) suggests that lean mass is logarithmically related to body fat. Thus, heavier individuals have greater lean mass, and because strength is related to mass, heavier individuals of all ages are also generally stronger when asked to perform simple tests of muscle strength. Viitasalo et al. (1985) demonstrated this using random samples of Finnish men drawn from three age groups: 31-35, and years of age. Although the older men had poorer isometric knee extension strength at each weight, within each age group, the heavier men had greater strength. In addition, it has been found that changes in body size will influence muscle mass, just as it influences levels of fat and bone. In a longitudinal study of change in urinary creatinine in 260 men aged 60 years or older from the Baltimore Longitudinal Study on Aging, those men who were heavier initially had greater baseline muscle mass. Over time, the entire group lost weight. Urinary creatinine declined with weight loss and was relatively constant across weight tertiles, suggesting that weight history will affect level of muscle mass as well as current weight (Muller et al. 1995). Lastly, despite the association with greater strength, heavier body weight is associated with poorer 13

22 functional health status (Launer et al. 1994), suggesting that the relationship of muscle to function may not be linear. In a study conducted by Sami Al-Abdulwahab (1998), he found that muscle strength and functional ability remained unchanged in the 20- and 30-year-old age groups. Around the age of 40, muscle strength and functional ability began to gradually decline. Stair-climbing, timed up-and-go and balance tests in the second decade were sec, sec, and sec, respectively, against sec, sec, and sec in the eighth decade. Statistical tests showed that muscle strength and functional ability displayed a significant relationship (p<0.001). If in fact LBM and strength are compromised during weight loss, additional research is warranted to determine the effect of these decrements on functional performance and the health related quality of life (HRQL). According to Fontaine et al. (1996), Obesity profoundly affects quality of life. Bodily pain is a prevalent problem among obese persons seeking weight loss and may be an important consideration in the treatment of this population. Therefore, it is the purpose of this study to detect changes in functional performance of overweight individuals during a 12 week period of weight loss. 14

23 III. METHODS This study examined the relationship between changes in both body weight and lean body mass and changes in muscular strength and function in overweight and obese adults. To examine these scientific questions the following methods and procedures were implemented. All procedures were approved by the Institutional Review Board (IRB) at the University of Pittsburgh, and written informed consent was obtained from all participants prior to their participation in this study. This study was conducted as a sub-study to a 12-week randomized clinical weight loss trial. This sub-study was 12-weeks in duration and provided an initial opportunity to examine changes in body weight, body composition, muscular strength, and functional ability. The main clinical trial did not systematically incorporate resistance exercise into the intervention, which allowed this substudy to examine the natural changes in muscular strength and functional ability independent of changes that may have resulted from resistance exercise training Subjects Seventy-five individuals with body mass index (BMI) ranging from 25.0 to 39.9 kg/m 2 (classified as overweight or obese) and age ranging from 18 to 55 years participated in this study. Randomization was performed blocking on gender (male and female) and BMI ( , , and kg/m 2 ). Individuals were excluded from participation based on the following criteria: 3.2. Exclusion Criteria 1. Reporting regular exercise participation of at least 20 minutes per day on at least 3 days per week during the previous six months. 2. Diabetes, hypothyroidism, or other medical conditions which would affect energy metabolism. 3. Women who are currently pregnant, pregnant within the previous six months, or planning on becoming pregnant within the next 18 months. 15

24 4. Non-medicated resting systolic blood pressure >160mmHg or non-medicated resting diastolic blood pressure >100mmHg, or taking medication that would affect blood pressure. 5. Taking medication that would affect resting heart rate of the heart rate response during exercise (e.g. beta blockade). 6. Arrhythmia on resting or exercise electrocardiogram that would indicate that vigorous exercise was contraindicated. 7. History of myocardial infarction or valvular disease. 8. Weight loss of >5% of body weight within the previous 12 months. 9. History of orthopedic complications that would prevent optimal participation in the exercise component (e.g., heel spurs, severe arthritis) Recruitment Subjects were recruited through a series of television, newspaper, radio, and direct mail announcements. Potential subjects were informed to contact the investigators at the University of Pittsburgh Physical Activity and Weight Management Research Center. Individuals were asked to participate in a brief telephone interview to determine initial eligibility. Eligible individuals were invited to attend a group orientation where they received a detailed description of the study. It was estimated that the orientation session would take minutes to complete. All participants interested in participating in the study completed a detailed medical history (Appendix A) and a physical activity readiness questionnaire (PAR-Q) prior to participating in this study (Appendix B). Participants also provided written clearance from their primary care physician (Appendix C) and written informed consent prior to participating in this study. Moreover, all participants completed a submaximal graded exercise test that was reviewed by a cardiologist as part of the baseline assessment for this study. 16

25 3.4. Experimental Design This study used a prospective observational design. All participants participated in a 12- week behavioral weight loss program that promoted a reduction in energy intake and an increase in energy expenditure in the form of aerobic exercise, primarily in the form of brisk walking. These intervention components are described in detail below. This study was a sub-study of a randomized clinical trial. The clinical trial involved individuals being randomized to one of three intervention conditions. The differences in the three interventions involved strategies to promote adherence to the aerobic exercise program. However, these interventions did not target changes in resistance exercise that may affect the outcome of this observational sub-study Intervention Components Eligible subjects were randomized to one of three intervention groups: 1) Standard In-Person Behavioral Weight Loss Program (SBWP): Subjects in this intervention group received an in-person standard behavioral weight control program following a clinical treatment model. 2) Intermittent Technology-Based Behavioral Weight Control Program (INT-TECH): Subjects in this group received all of the components included in the SBWP; however, individuals in this intervention group utilized the HealthWear System during weeks 1, 5, and 9 of the intervention period. 3) Continuous Technology-Based Behavioral Weight Control Program (CON-TECH): Subjects in this group received all of the components included in the SBWP; however, individuals in this intervention group utilized the HealthWear System daily throughout the intervention period. 17

26 Intervention Contact Subjects in all groups (SBWP, INT-TECH, CON-TECH) received an in-person standard behavioral weight control program that followed a clinical treatment model. The in-person visits were conducted in an individual session by a trained interventionist. During the in-person sessions the interventionist integrated behavioral strategies to assist with weight control. Body weight was measured at each in-person session, with subjects being encouraged to monitor their body weight on their own during weeks when no in-person visits were scheduled. All sessions were conducted at the Physical Activity and Weight Management Research Center at the University of Pittsburgh Behavioral Lesson Content All in-person visits focused on a specific behavioral topic related to weight loss, eating behaviors, or exercise behaviors (See Table 3.1). The interventionist facilitated a discussion related to the specified topic. At each visit, participants were also provided written material as a supplement. During weeks that subjects did not attend an in-person session, they were mailed a behavioral lesson to offer a form of consistent weekly contact and support. 18

27 Table 3.1. Behavioral Lesson Titles Week Number Delivery Format Lesson Title 1 IP Behavioral approach to changing eating and exercise habits 2 IP Healthy food choices 3 IP Developing and implementing an exercise program 4 IP Motivation 5 M Energy balance 6 IP Food guide pyramid/portion control 7 M Stimulus control/urge management 8 IP Exercise barriers 9 M Eating out 10 IP Evaluating progress/looking ahead 11 M Problem solving 12 M My time, my values IP = in-person lesson; M = mailed lesson 3.6. Dietary Intervention Subjects were instructed to reduce calorie intake to calories per day based on body weight (<200 pounds = 1200 kcal/day; pounds = 1500 kcal/day; >250 pounds = 1800 kcal/day) and to reduce fat intake to 20-25% of total dietary intake. Subjects were provided with sample meal plans and menus to assist them with making appropriate food selections, and these were developed by registered dietitians. Subjects recorded their eating behaviors in a weekly food diary (SBWP) or on the HealthWear System website (INT-TECH and CON-TECH) that was reviewed weekly by the intervention staff. Subjects participating in eating behaviors inconsistent with the recommendations for this study were counseled by the registered dietitian affiliated with this study Exercise Recommendations All subjects were instructed to exercise at a moderate intensity on 5 days per week. Initially subjects were instructed to exercise 20 minutes per day, this duration was gradually progressed to at least 40 minutes per day. The exercise progression was 10 minutes per day in 4 week intervals. Subjects were encouraged to participate in activity that is at minimum moderate in intensity, with an 19

28 RPE set at on the 15-point Borg scale and/or heart rate range between 55-70% of maximal heart rate. Activities that were consistent with this intensity level are similar to brisk walking Assessments Procedures All subjects participated in assessments at baseline and following 12-weeks of weight loss treatment. These assessments included the following procedures which provided the data for this study. Weight: Body weight was assessed using a calibrated balance-beam scale. Subjects were clothed in a light-weight cloth hospital gown, and weight was measured to the nearest 0.25 pounds. Height: Height was measured using a wall-mounted stadiometer without the subject wearing shoes. Height was measured to the nearest 0.1 centimeter. Body Mass Index (BMI): Body mass index was computed from measurements of weight and height (kg/m 2 ). Body Composition: Body composition was assessed using an RJL bioelectrical impedance analyzer (BIA) which provided an estimate of lean body mass and body fatness using the equation proposed by Segal (1988). Subjects were instructed to fast, except for water, for at least 4 hour prior to this assessment. Muscular Strength: Muscular strength was assessed using a 1-repetition maximal (1-RM) test. A Zuma Universal Gym was used to perform the 1-RM test. Upper body muscular strength was assessed using the chest press exercise, with lower body strength assessed using the leg extension exercise. The following specific procedures were used when performing these assessments. ACSM guidelines for 1-RM testing were followed accordingly to determine muscular strength using the vertical chest press. The subject was seated at the machine with feet flat on the 20

29 floor and back against the support pad. Both hands were in a neutral grip position grasping the handles located at chest level. A complete repetition was constituted as a lift where the subject s arms were extended in front of them until their elbows were approximately 5º short of full extension and then returned back to the starting position. The subject first warmed-up with 5-10 repetitions at 40-60% of their perceived maximum. Following a one minute rest with light stretching, the subject performed 4-5 repetitions at 60-80% of their perceived maximum. Then a small amount of weight was added, and a 1-RM lift was attempted. If the lift was successful, a rest period of 1-2 minutes was provided. The goal was to find the 1-RM within 3-5 maximal efforts. The 1-RM was reported as the weight of the last successfully completed lift (ACSM s Guidelines for Exercise Testing and Prescription. 6 th edition, 2000). The test-retest reliability of the 1-RM test varies from (Faigenbaum et al). ACSM guidelines for 1-RM testing were followed accordingly to determine muscular strength using the leg extension. The subject was seated at the machine with back against the support pad, knees in alignment with the pivot point of the machine, and ankles behind the ankle pad. The subjects were instructed to extend their knees as fully as possible, from 90º of flexion to full extension, then to return to their starting position. A complete repetition was constituted as a lift where the subject s legs were extended to their full range of motion (determined in the unweighted position) and then returned back to the starting position. The subject first warmed-up with 5-10 repetitions at 40-60% of their perceived maximum. Following a one minute rest with light stretching, the subject performed 4-5 repetitions at 60-80% of their perceived maximum. Then a small amount of weight was added, and a 1-RM lift was attempted. If the lift was successful, a rest period of 1-2 minutes was provided. The goal was to find the 1-RM within 3-5 maximal efforts. The 1-RM was reported as the weight of the last successfully completed lift (ACSM s Guidelines for 21

30 Exercise Testing and Prescription. 6 th edition, 2000). The test-retest reliability of the 1-RM test varies from (Faigenbaum et al). Function: The sit-to-stand test, a test generally used in the geriatric population, was used to assess lower-body strength and functional performance (Bohannon et al, 1995, Rikli et al, 1999, & Jones et al, 1999). The participant was instructed to sit in the middle of a chair with his or her back straight, feet flat on the floor, and arms crossed at the wrists and held against the chest. The participant rose to a full stand and then returned to a fully seated position as many times as he or she could in 30 seconds. Participants were instructed not to use momentum or their hands to assist them to a fully standing position. The score was recorded as the number of stands completed in 30 seconds. If the participant was more than halfway up at the end of 30 seconds, it was counted as a full stand. Before the test was performed, a verbal description and a visual demonstration was provided. Each of the participants practiced the movement to minimize the effect of a learning curve from pre to post test. Physical Activity: Physical activity was assessed using the questionnaire developed by Paffenbarger and colleagues for the Harvard Alumni Study (1978, 1986). This questionnaire provided an estimate of energy expenditure per week of activities performed during leisure-time which may include exercise, sports, and other forms of recreation. In addition, this questionnaire included walking and stair climbing. This questionnaire is provided in Appendix D Data Analysis Data analysis were conducted using SPSS statistical software, with statistical significant defined as p<0.05. Data were entered into an Access Database and converted to the appropriate file for data analysis. The data were initially analyzed using descriptive statistics, which included mean, standard deviation, range, and tests for normal distribution of the data. Data were also analyzed using dependent t-tests to determine if the outcomes measures in this study changed significantly 22

31 over the 12 weeks of treatment. One-way analysis of variance (ANOVA) was used to determine if there were differences in the change in the outcome variable based on randomized group assignment. The primary and secondary hypotheses were tested using correlation coefficients. Pearson Product Moment correlation coefficients were used for data analysis when the data were considered to be normally distributed. However, when data were found to be skewed, Spearman Rank Order correlation coefficients were used Power Analysis The primary and secondary hypotheses in this study were examined using correlation coefficients. Because on this, the power analysis was conducted based on the ability to detect significant correlations between the variables of interest. Thus, the power analysis was conducted to determine if the 75 subjects available for this study would provide adequate statistical power to examine the primary hypotheses in this study. Based on an available sample of 75 subjects, and assuming the possibility of 15 percent attrition, this would allow for 64 subjects to complete this study. This sample size allowed for correlations of 0.40 to be detected with at least 0.95 statistical power. Moreover, this sample size allowed for 0.80 statistical power to detect a correlation of 0.30 in this study. 23

32 IV. RESULTS The purpose of this study was to examine the relationship between changes in body weight and lean body mass and changes in muscular strength and function during a 12 week weight loss intervention in overweight and obese adults. This study was a pretest-posttest clinical weight loss intervention with assessments performed at 0 and 12 weeks of participation. The primary dependent variables were body weight, body mass index (BMI), body composition, strength (1-RM chest press, 1-RM leg extension, grip strength), and function (sit-to-stand) Subject Characteristics The subjects in this investigation were 57 adults (1 male, 56 females). Eligible subjects were between 21 and 55 years of age, with a BMI ranging from 25.0 to 39.9 kg/m 2. Descriptive characteristics are presented in Table 4.1. To examine if the results of the one male subject in this study influenced the results, the statistical analyses were performed with and without the male subject. There was no difference in the pattern of the results when the male subject was included in the analyses, and therefore the results are presented which include the male subject. Table 4.1 Characteristics of Subjects at Baseline Variable Total (N = 57) Completers (N = 50) Non-Completers (N = 7) Age (years) * Height (cm) Weight (kg) % Minority 38.6 (N=22) 32.0 (N=16) 85.7 (N=6) BMI (kg/m 2 ) Body comp.(% fat) RM Leg (kg) RM Chest (kg) Grip Strength Right Hand (kg) Grip Strength Left Hand (kg) **Sit-to-Stand (reps) * Indicates statistical significance between Completers and Non-Completers at p<0.05. **Number of sit-to-stands performed in 30 seconds. 24

33 4.2. Retention Rates A total of 50 subjects (88% of all subjects) provided objective weight data at baseline and 12 weeks; these subjects were referred to as completers. Those subjects not providing objective data at baseline and 12 weeks are referred to as non-completers (N=7, 12% of all subjects), with study withdrawal resulting from the subject electing to discontinue participation for unknown reasons (N = 5) or as a result of conflicting family issues (N = 2). In addition, because of non-study related physical injuries (i.e. knee pain, wrist sprains, surgery) at the 12-week assessment, 6 participants were unable to perform the 1-RM leg extension, 5 participants were unable to perform the 1-RM chest press, 3 unable to perform the grip strength test, and 3 unable to perform the sit-to-stand test. See Figure 4.1 for assessment completion details. 25

34 Figure 4.1 Assessment Completion at baseline and 12 weeks 57 Subjects 1-RM Leg Extension 1-RM Chest Press Grip Strength - RH Grip Strength - LH Sit-to-Stand 7 withdrew 5 Dropped out 2 Family Issues 7 withdrew 5 Dropped out 2 Family Issues 7 withdrew 5 Dropped out 2 Family Issues 7 withdrew 5 Dropped out 2 Family Issues 7 withdrew 5 Dropped out 2 Family Issues Incomplete data 6 Physical Injuries Incomplete data 5 Physical Injuries Incomplete data 3 Physical Injuries Incomplete data 3 Physical Injuries Incomplete data 3 Physical Injuries 44 completed 12-week Trial 45 completed 12-week Trial 47 completed 12-week Trial 47 completed 12-week Trial 47 completed 12-week Trial 26

35 4.3. Absolute and Relative Changes Absolute and Relative Change in Body Weight and Lean Body Mass To examine the specific aims related to the effect of the intervention on body weight and lean body mass (LBM), a series of paired sample t-tests were performed. There was a significant reduction in absolute body weight ( kg; p < 0.001) and relative weight loss ( %; p<0.001). In addition, there was a significant reduction in absolute LBM (0.8 kg kg; p = 0.002) and relative LBM loss ( %; p<0.001) with fat mass decreasing by kg (p<0.001). Percent body fat decreased from % at baseline to % at the completion of the intervention (p<0.001) Absolute and Relative Change in Strength and Function To examine aims related to the effect of the intervention on muscular strength and function, a series of paired sample t-tests were performed. These results are shown in Table 4.2. Absolute loss in leg and chest strength was kg (p<0.001) and kg (p = 0.003), respectively. The relative loss of leg and chest strength was % (p<0.001) and % (p<0.001) respectively. Although not statistically significant, grip strength decreased by 0.5 kg kg ( %) (p = 0.37). Functional testing included the sit-to-stand test and this increased by stands ( %) (p = 0.05) across the 12 week intervention Absolute and Relative Change in Leisure-Time Physical Activity To examine the aim related to the effect of the intervention on leisure time physical activity, a paired sample t-test was performed. These results are shown in Table 4.2. Absolute increase in leisure time physical activity was kcal/wk (p<0.002) and relative increase was kcal/wk (p<0.002) across the 12 week intervention. Baseline and 12 week leisure-time physical activity data were examined to determine the prevalence of subjects participation in resistance exercise. At baseline, 23 sessions were reported 27